Why am I putting on weight?

I am 14 I eat right and I am also doing Marathon training. I have been running for a very long time like a over a year, but I just started the 16 week marathon training like 4 weeks ago. I am getting over from almost becoming anorexic by not eating and exercising aggressively. Now I am just putting on weight everybody says I'm not fat, but all I see is fat @_@. please help.